Generated dart code should import transitive imports.

mojo/dart/packages/_mojo_for_test_only/lib/test/pingpong_service.mojom.dart

Index: mojo/dart/packages/_mojo_for_test_only/lib/test/pingpong_service.mojom.dart
diff --git a/mojo/dart/packages/_mojo_for_test_only/lib/test/pingpong_service.mojom.dart b/mojo/dart/packages/_mojo_for_test_only/lib/test/pingpong_service.mojom.dart
index 5463c642e2bedb4d65e40d410d8b24c0ab7a7bbb..d9a8e266610296a9e7e6af3e177163934f4a5232 100644
--- a/mojo/dart/packages/_mojo_for_test_only/lib/test/pingpong_service.mojom.dart
+++ b/mojo/dart/packages/_mojo_for_test_only/lib/test/pingpong_service.mojom.dart
@@ -1231,7 +1231,7 @@ mojom_types.RuntimeTypeInfo  _initRuntimeTypeInfo() {
   // serializedRuntimeTypeInfo contains the bytes of the Mojo serialization of
   // a mojom_types.RuntimeTypeInfo struct describing the Mojom types in this
   // file. The string contains the base64 encoding of the gzip-compressed bytes.
-  var serializedRuntimeTypeInfo = "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";
+  var serializedRuntimeTypeInfo = "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";
 
   // Deserialize RuntimeTypeInfo
   var bytes = BASE64.decode(serializedRuntimeTypeInfo);